Spinning Fruits
Technical & Teaching Notes
Related sheets
Falling from trees; Coconuts; Parachuting fruits; Gliding fruits; One-winged fruits; Two-winged fruits
Introduction and context
Heavy fruits fall directly to the ground. Some may roll away - if a tree is growing on a slope, for
example - but most rely on animals or water (rivers, streams and oceans) to disperse them. Other
fruits are smaller and lighter. They have shapes that help ensure that wind will disperse them.
They are called winged fruits and there are several types. Parachute fruits do not have wings.
However, when some fruits dry out, they produce paper thin, rigid wings. The dried fruit is called a
samara. Their structure has evolved to enable seeds to be carried further and be spread more
widely by the wind. Seeds from conifer cones also have wings.
This activity is more about ‘physics and maths’than ‘biology’. However, it is designed to help
students understand the evolution of winged fruits. The activities in this sheet could be used
alongside any of the other sheets in Seed dispersal.
Possible barriers to learning
The session allows a number of common misconceptions associated gravity and objects falling to
Earth. Depending on the nature of discussions with students, misconceptions that could be
addressed include:

gravity = ‘downness’

when an object is stationary, no forces are acting on it

heavy objects fall faster than light objects

something stops moving because the force has run out

air doesn’t weigh anything

particles are the same as visible grains as in rocks, for example.
Links to National curriculum for science in England at key stage 3
In biology pupils should be taught about reproduction, which includes:

reproduction in plants, including flower structure, wind and insect pollination, fertilisation,
seed and fruit formation and dispersal, including quantitative investigation of some dispersal
mechanisms
In physics pupils should be taught about forces, pressure in fluids and forces and motion. This
includes:

forces as pushes or pulls, arising from the interaction between two objects

using force arrows in diagrams, adding forces in one dimension, balanced and unbalanced
forces

forces: with pushing things out of the way; resistance to motion of air and water

non-contact forces: gravity forces acting at a distance on Earth and in space

atmospheric pressure, decreases with increase of height as weight of air above decreases
with height

pressure in liquids, increasing with depth; upthrust effects, floating and sinking
Science & Plants for Schools: www.saps.org.uk
Spinning Fruits: p. 1

forces being needed to cause objects to stop or start moving, or to change their speed or
direction of motion (qualitative only)

change depending on direction of force and its size
Safety Notes
Activities that make up this resource use no harmful materials or equipment other than scissors or
possibly scalpels or sharp knives for cutting paper.
Equipment and materials
Each student or group will need:

3 or 4 sheets of A4 paper (ideally white one side and coloured the other)

pencil, ruler and scissors

3 cm long paper clip

optional: (a) stopwatch to time descents, (b) smartphone/digital camera to video the descent
Teaching Notes
Activity 1: Nature’s designs
When looking at the photographs help students, if they need it, to locate the position of the seed
in the fruit. They might also be encouraged to search the Internet for other examples of winged
fruit.
Answer
Seed in centre of wing: Hoptree and Bushwillow
Seed at end of single wing: Maple and Ash
Seed attached to two wings: Dipterocarpus obtusifolius and Dipterocarpus alatus
It’s a coincidence that the names of both two-winged fruits are in italics (signifying that this is the
Latin botanical name).
Activity 2: Design matters
This part of the activity is about shape and the way an object falls. You may need to spend a little
time explaining the terms ‘line of reflective symmetry’ and ‘centre of mass’ (or ‘centre of gravity’ –
the two terms are interchangeable).
The KS3 maths curriculum requires that students are able to identify properties of, and describe
the results of, translations, rotations and reflections applied to given figures. Centre of mass might
be introduced by talking about and demonstrating the idea of a ‘balance point’. This is
straightforward with shapes cut from sheets of paper or card, but a little more difficult with threedimensional objects.
Science & Plants for Schools: www.saps.org.uk
Spinning Fruits: p. 2
Answers
1. All shapes spin (using paper coloured on one side and white on the other makes this very
clear, but it isn’t essential). Depending on where they are held before release they may flutter
before orientating themselves and then spinning.
2. Students should be able to do this, but help them if necessary – it isn’t a maths test!
3. They spin along their longest line of reflective symmetry.
4. The two rectangles B and C, especially the longer one (C), may also begin to spiral gently as
well as spin.
Remind students of the two opposing forces when something falls to the ground – gravity and air
resistance.
Activity 3: More design matters
Winged fruit with the seed in the middle of the wing, e.g. Bushwillow and Hoptree, are much the
same as a paper circle, but with a small mass at the centre. They fall to the ground in the same
way that the paper circle did. Students could try this out.
However, other winged fruits do not have shapes that correspond to shape A-D. This part of the
activity is about exploring others shapes that are more like winged fruits.
Answers
1. Shapes E, G and H.
2. Shapes F, I and J. All spun, but also spiralled.
3. Shapes E, G and H have two or more lines of reflective symmetry. Shapes F, I and J have only
one line of reflective symmetry.
4. All shapes are pulled to ground by the force of gravity. However, they need to push air particles
out of the way as they fall. This causes the shapes to behave in various ways – spinning and
spiralling.
Activity 4: Getting closer to a one-winged fruit
Ask students about the differences between the cut-out paper shapes I and J and a single winged
fruit such as Ash or Maple. If necessary, guide them to the idea that the position of the seed
means that the centre of mass is moved towards one end of the wing.
Answers
1. It will spin and quite soon begin the spiral rapidly.
2. The spiralling is much faster.
3. The centre of mass is much closer to one end.
4. Any suitable sentence that captures the ideas of spin, spiralling and rotating.
Science & Plants for Schools: www.saps.org.uk
Spinning Fruits: p. 3